In the process of traditional water treatment, the humic acid and fulvic acid can be oxidized by chlorination; besides, it also produces small molecular organic compounds at the same time. Coagulation, flocculation, and sedimentation can reduce the concentration of the Assimilable Organic Carbon (AOC) significantly. An example of Ping-Ding water treatment plant was performed with sampling twelve times monthly from December 2008 to November 2009, the strong influence of chlorine, and coagulation, flocculation on the AOC can be observed. Comparing to the removal efficiency of water process in Ping-Ding water treatment plant, the AOC presented much stably in the distribution systems. We observed the data on the mean concentration of monthly sampling related to the operation unit in the water treatment plant. The Total Organic Carbon (TOC), and the Dissolved Organic Carbon (DOC) had the same trend with AOC in the water treatment process; it showed that TOC, and DOC had well relation to AOC in Ping-Ding water treatment plant. However, scrutinizing single monthly sampling, we found that the concentration of AOC did not fix out with the concentration of TOC and DOC at the same time. Therefore, results indicate that the AOC is mainly related to the smaller organic molecules of the TOC. In the series of sampling, we divided the influence of climate factor into the dry season and the pour season. The research discussed the five analysis items in the final results and discussion¡GTOC, DOC, UV254, UV254/DOC, and AOC. Basically, the concentration of the five analysis items on the pour season is higher than the dry season; it indicates that the raw water¡¦s concentration of organic carbon in Ping-Ding water treatment plant is higher during raining days. This can express the high concentration of the UV254, UV254/DOC, and AOC in water treatment plant in our work.

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Introdução: Organismos pertencentes ao gênero Aeromonas estão amplamente distribuídos no ambiente aquático sendo atualmente considerados como patógenos emergentes. Estudos demonstraram que, estes podem produzir uma série de fatores de virulência, e ainda um maior número de casos clínicos vêm sendo confirmados e atribuídos às diferentes espécies de Aeromonas. Objetivo: Estudar a ocorrência do gênero Aeromonas em efluentes de um sistema de lagoas de estabilização e discutir o significado da presença destes para a saúde pública. Métodos: A determinação de Aeromonas spp foi realizada pela técnica de tubos múltiplos (NMP/100 mL). Para a verificação da presença e ausência (PA) as colônias foram isoladas em ágar sangue ampicilina, ágar amido ampicilina e ágar MacConkey. As colônias que apresentaram resultados presuntivos para o grupo Aeromonas foram submetidas ao reisolamento em Ágar Amido, e a provas bioquímicas para identificação das espécies. O perfil plasmidial foi realizado de acordo com a metodologia descrita por BIRNBOIN & DOLLY 1979. Resultados: Aeromonas spp foram isoladas em 72,4% e 55,1% das amostras provenientes da entrada e saída da lagoa anaeróbia respectivamente, e em 48,3% da saída da lagoa facultativa variando as contagens entre <3 e 3,0x109 NMP/100mL. Na unidade de desinfecção por cloro entre <3 e 9,0 x 105 NMP/mL Conclusões: Observou-se que embora haja uma tendência de decaimento nas contagens de Aeromonas, não é possível eliminá-las do sistema estudado, mesmo após cloração. Esses organismos podem representar um risco à saúde devido à seleção de cepas resistentes que são lançadas no meio ambiente. / Introduction: Organisms of the genus Aeromonas are widely distributed in the aquatic environment, being now considered emerging organisms. Studies show that these organisms can produce a series of virulence factors, and that a major number of clinic cases have been confirmed and attributed to the different species of Aeromonas. Objective: Study the occurrence of the genus Aeromonas in effluents of a stabilization ponds system and discuss the meaning of the presence of these organisms for public health. Methods: Aeromonas spp determination was carried out by the most probable number technique (NMP/100mL). To verify the presence or absence, the colonies were isolated in ampicilin blood agar, starch agar, and Mc Conkey agar. Colonies showing presumptive results for Aeromonas group were re isolated in starch agar and to biochemical tests to identify the specie. The plasmidial profile was carried out according to the methodology described by BIRNBOIN & DOLLY 1979. Results: Aeromonas spp were isolated in 72,4% and 55.1% of the samples from the afluent and the end of anaerobic lagoons, respectively, in 48.3% of the effluent of the facultative lagoon in counts that varied from <3 and 3.0x109 NMP/100mL. In the disinfection unit counts varied from <3 and 9.0x105 NMP/100mL. Conclusions: It was possible to observe that even though a tendency of decaiment was noted for the counts of Aeromonas, it was not possible to totally eliminate this organisms from the studied system, even after the chlorination. These organisms could pose a health risk due to the selection of resistant strains released in the environment

Introdução: Organismos pertencentes ao gênero Aeromonas estão amplamente distribuídos no ambiente aquático sendo atualmente considerados como patógenos emergentes. Estudos demonstraram que, estes podem produzir uma série de fatores de virulência, e ainda um maior número de casos clínicos vêm sendo confirmados e atribuídos às diferentes espécies de Aeromonas. Objetivo: Estudar a ocorrência do gênero Aeromonas em efluentes de um sistema de lagoas de estabilização e discutir o significado da presença destes para a saúde pública. Métodos: A determinação de Aeromonas spp foi realizada pela técnica de tubos múltiplos (NMP/100 mL). Para a verificação da presença e ausência (PA) as colônias foram isoladas em ágar sangue ampicilina, ágar amido ampicilina e ágar MacConkey. As colônias que apresentaram resultados presuntivos para o grupo Aeromonas foram submetidas ao reisolamento em Ágar Amido, e a provas bioquímicas para identificação das espécies. O perfil plasmidial foi realizado de acordo com a metodologia descrita por BIRNBOIN & DOLLY 1979. Resultados: Aeromonas spp foram isoladas em 72,4% e 55,1% das amostras provenientes da entrada e saída da lagoa anaeróbia respectivamente, e em 48,3% da saída da lagoa facultativa variando as contagens entre <3 e 3,0x109 NMP/100mL. Na unidade de desinfecção por cloro entre <3 e 9,0 x 105 NMP/mL Conclusões: Observou-se que embora haja uma tendência de decaimento nas contagens de Aeromonas, não é possível eliminá-las do sistema estudado, mesmo após cloração. Esses organismos podem representar um risco à saúde devido à seleção de cepas resistentes que são lançadas no meio ambiente. / Introduction: Organisms of the genus Aeromonas are widely distributed in the aquatic environment, being now considered emerging organisms. Studies show that these organisms can produce a series of virulence factors, and that a major number of clinic cases have been confirmed and attributed to the different species of Aeromonas. Objective: Study the occurrence of the genus Aeromonas in effluents of a stabilization ponds system and discuss the meaning of the presence of these organisms for public health. Methods: Aeromonas spp determination was carried out by the most probable number technique (NMP/100mL). To verify the presence or absence, the colonies were isolated in ampicilin blood agar, starch agar, and Mc Conkey agar. Colonies showing presumptive results for Aeromonas group were re isolated in starch agar and to biochemical tests to identify the specie. The plasmidial profile was carried out according to the methodology described by BIRNBOIN & DOLLY 1979. Results: Aeromonas spp were isolated in 72,4% and 55.1% of the samples from the afluent and the end of anaerobic lagoons, respectively, in 48.3% of the effluent of the facultative lagoon in counts that varied from <3 and 3.0x109 NMP/100mL. In the disinfection unit counts varied from <3 and 9.0x105 NMP/100mL. Conclusions: It was possible to observe that even though a tendency of decaiment was noted for the counts of Aeromonas, it was not possible to totally eliminate this organisms from the studied system, even after the chlorination. These organisms could pose a health risk due to the selection of resistant strains released in the environment

Bacteriophages are viruses that specifically infect bacteria. The bactericidal nature of lytic bacteriophages has been exploited by scientists for decades with the hope to utilise them in the fight against bacterial infections and antibiotic resistant bacteria in medical settings. More recently, the potential applications of bacteriophages for biocontrol in the agrifood and environmental sectors have been investigated in an attempt to develop ‘natural’ antimicrobial products. Bacteriophages have a couple of decisive advantages over conventional methods of controlling pathogenic bacteria, such as high host specificity, the ability to self-replicate, and the ability to evolve with their hosts. However, more research is needed to optimise the parameters for phage applications, including the impact of environmental conditions on lysis efficiency, multiplicity of infection, and to significantly minimise the emergence of bacterial resistance to phages. Temperature plays a key role in every biological activity in nature. It is also assumed that temperature has an effect on phage lysis efficiency. A comprehensive study of it and how it affects both the host cells and their corresponding phages is crucial to ensure the efficient removal of bacterial pathogens. In this thesis, temperature (as selected parameter) was investigated to determine its influence on the lysis effectiveness of the three different phages belonging to the family of the Myoviridea that were isolated and purified from a single water sample taken from a brook receiving treated wastewater. We used the multiplicity of infection of 1 in all of our study in this project. Temperature was found to have a significant impact on phage-mediated lysis efficiency. Both the temperature of incubation of the phage-bacteria mixture (incubation temperature) and the temperature history of bacterial hosts were found to have profound effects on plaque sizes as well as plaque numbers. Plaque size and number decreased with increasing temperature. For the phages examined, bacterial lysis was more efficient at 20°C compared to 30 or 37°C. Phages were suggested to be well adapted to the environment where they were isolated from with general implications for use in biological disinfection. Furthermore, the temperature history of the bacteria (prior to phage encounter) was found to have a modulating effect on their susceptibility to lysis. A second part of this study compared the performance of the three phages in regard to bacterial resistance. The emergence of bacterial resistance is a major obstacle to the success of bacteriophages applications. The use of multiple phages is typically recommended and has proven better than the use of a single phage. However, the bestway to perform phage treatment is still very unclear. This study therefore compared simultaneous addition of multiple phages (in form of a cocktail) with the sequential addition of the individual phages at different time points in trying to delay the emergence of bacterial resistance. The data obtained from this work suggest that lysis effectiveness can be adjusted to optimize any treatment goal. For fast initial bacterial clearance the use of a single phage with short time maximal lysis efficiency proved most efficient, while the simultaneous addition of phages in the form of a cocktail was most successful strategy in our study. Addition of selected phages sequentially can be normalized in such a way that is just as effective as a cocktail. A third part of this thesis looked into the susceptibility of bacteria that had undergone sublethal disinfection. We addressed the question whether bacteria subjected to sublethal doses of chlorine and UV are still susceptible to phage-mediated lysis. The chlorine treatments indicated the development of a phage-insensitive phenotype for a critical chlorine dose in the transition zone between live and dead. The remaining live (and culturable) bacteria were shown insensitive to the selected phage. The lowest UV exposure at 2.8 mJ/cm2 eliminated bacteria susceptibility to the phages. This phage- resistant phenotype may have serious consequences for the application of phages on foods or water that have previously undergone a weak disinfection regime.

Chlorine has effectively reduced the prevalence of waterborne diseases, however there are secondary consequences to this public health advancement. Disinfection byproducts (DBPs) are chemicals formed when chlorine reacts with natural organic matter (NOM) in water. A new class of DBPs, halobenzoquinones (HBQs), has recently been identified and data suggests it could be potentially carcinogenic and up to 1000 times more toxic than some regulated DBPs. So far, in vitro studies have assessed HBQ toxicity without taking into account its transformation in cell media into potentially less toxic compounds. This study evaluated the toxic effects of one HBQ, 2,6-DCBQ, and its transformed derivatives on colon epithelial and liver hepatoma cell lines by measuring intracellular reactive oxygen species production and cell viability post-DCBQ exposure. In addition, to better quantify the trade-off between exposure to waterborne pathogens and 2,6-DCBQ, the inactivation of a virus indicator (MS2), and formation of DCBQ were determined in chlorinated surface waters. Dose-dependent toxic effects were observed in both cell lines and transformed DCBQs were observed to be less toxic than their parent compound. MS2 inactivation occurred immediately post-chlorination, but DCBQ was detected simultaneously. Such findings indicate that this compound is toxic to human cells, including colon epithelial cells, which may be pertinent due to the possible association between chlorinated waters and colon cancer. Findings also suggest this DBP may be relevant in developing countries because HBQs may form in point-of-use chlorinated drinking waters. Furthermore, observed reduction in toxicity of media-transformed DCBQs calls current literature on HBQ toxicity into question.